1. Field of the Invention
The present invention relates to wireless communication devices and particularly relates to wireless communication devices preferably use in radio frequency identification (RFID) systems.
2. Description of the Related Art
In recent years, as merchandise information management systems, RFID systems have been implemented in which communication using a non-contact method employing an electromagnetic field is performed between a reader/writer that generates an induction magnetic field and an RFID tag (also referred to as a wireless communication device) attached to a piece of merchandise so as to transmit predetermined information therebetween. Such an RFID tag includes a wireless IC chip that stores predetermined information and processes a predetermined wireless signal, and an antenna that transmits and receives a high-frequency signal.
As an antenna used in such an RFID tag, dipole antennas such as those described in Japanese Unexamined Patent Application Publication No. 2004-104344, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-524363 and International Publication No. 2007-013168 are known. Dipole antennas can secure a comparatively large communication range, but have a problem in that they have a large size. In recent years, there has been a demand to “reduce RFID tags in size, despite this reducing the communication range somewhat”, but it has been difficult to respond to and satisfy this demand using conventional dipole antennas.